Right-Turn Traffic Volume Adjustment in Traffic Signal Warrant Analysis

An intersection with heavy right-turn volumes, without any reduction, might mislead a signal warrant analysis, and a different conclusion may be reached on whether a signal is warranted. Previous right-turn volume reduction methods based mostly on engineering judgment lack specific theoretical backgrounds. Therefore, this paper proposes a new method with theoretical justification. The method focuses on traffic operation principles centered on finding the delay equivalent relationship between right-turn and through traffic, that is, to equate the right-turn volume to through vehicles to produce the same control delay on a minor street. Equivalent factor tables were constructed on the basis of four geometric configurations. Combining with the various traffic volume distributions, more than 12,000 scenarios were analyzed. The volume ratio in the two directions of the main street was especially considered. The analysis showed that the uneven volume distribution in the main street had a greater effect on the minor-street right-turn movement. To use the equivalent factors efficiently, statistical regression models were developed. Last, the proposed method was applied to one signal warrant case and demonstrated promising results for its practical application in traffic signal warrant analysis.